What is the correct structure for transition metal complex ions?

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Discussion Overview

The discussion revolves around the structural geometry of transition metal complex ions, specifically focusing on the compound [CoCl4]. Participants explore the possible tetrahedral and square planar arrangements of the complex, considering the implications of ligand repulsion and bond angles.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant expresses confusion about the 3-D structure of [CoCl4], noting the existence of two proposed geometries: tetrahedral and square planar.
  • Another participant suggests that a tetrahedral shape might be correct due to the four chloride ions repelling each other, which would maximize their distance apart.
  • A later reply references a previous discussion on the same topic, indicating that the participant should revisit that response for additional insights.
  • One participant acknowledges that the previous explanation was complex but concludes that they do not need to focus on it for their exam, suggesting a level of uncertainty about the topic.
  • Another participant reassures that for an introductory chemistry class, understanding the VSEPR theory may suffice, while noting that the distinction between the two geometries is a more advanced topic.

Areas of Agreement / Disagreement

Participants do not reach a consensus on which structure is correct for [CoCl4]. Multiple competing views regarding the geometry remain, with some favoring tetrahedral and others acknowledging the possibility of square planar.

Contextual Notes

There is a noted complexity in the discussion, with references to prior posts and the suggestion that the topic may be beyond the current level of understanding for some participants. The discussion also highlights the difference in depth of knowledge required for introductory versus advanced chemistry courses.

Who May Find This Useful

This discussion may be useful for students studying introductory chemistry or those interested in the structural properties of transition metal complexes.

joeyjo100
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I'm getting myself muddled up, and don't know how to work out what the 3-d structure of transition metel complex ions.

For example, the compound [CoCl4] has a Cobalt +2 ion surrounded by four chloride ions. I've seen two different structures for it. One is tetrahedral, like methane, the other is sqaure planar.

Which structure is correct?
 
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Which one do you think is correct, based on your own analysis?
 
well i would have guessed a tetrahedral shape for [CoCl4], just because there are 4 chloride ions, which would try and repel each other as much as possible.

The tetrahedral shape has a bond angle of 109 degrees compared to 90 degrees for a square planar shape, so this allows the greatest distance for the chloride ligands
 
joeyjo100 said:
well i would have guessed a tetrahedral shape for [CoCl4], just because there are 4 chloride ions, which would try and repel each other as much as possible.

The tetrahedral shape has a bond angle of 109 degrees compared to 90 degrees for a square planar shape, so this allows the greatest distance for the chloride ligands

Ok .. that's a reasonable start. However you asked a similar question about square-planar vs tetrahedral geometries before, and I answered it. Why don't you go back to that response, and see if it gives you some additional insight.
 
yeah. I forgot that I'd posted that, I've been in my own little revision world lately so things just keep coming and going.

And in fact I just looked back at the reply in my last post. I do admit that it's a bit over my head, but I guess that in itself is an answer. It means that I don't need to be worrying too much about it for the exam.

thanks for replying!
 
joeyjo100 said:
yeah. I forgot that I'd posted that, I've been in my own little revision world lately so things just keep coming and going.

And in fact I just looked back at the reply in my last post. I do admit that it's a bit over my head, but I guess that in itself is an answer. It means that I don't need to be worrying too much about it for the exam.

thanks for replying!

No problem ... sorry if my reply was over your head. Please feel free to ask if you need or want clarification on any of the points. If you are in an introductory chemistry class, then it is likely that you only need to know the VSEPR arguments that you gave above in #3 to explain the structure. The difference between square-planar and tetrahedral geometries for coordination complexes is a more advanced topic that you will hit when you study inorganic chemistry at a higher level.
 

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